Filter Cartridge with Pressure Relief Valve

ABSTRACT

A filter cartridge includes a substantially cylindrical filter media and a pressure relieving structure. The filter media is adapted to allow fluid to pass from an exterior of the filter media to an interior space of the filter media. The pressure relieving structure is disposed at an upper end of the filter media, and the pressure relieving structure opens when a predetermined pressure level is established across the filter media to maintain the predetermined pressure across the filter media.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 11/581,856, which is a divisional of U.S. patent applicationSer. No. 11/027,168, filed Dec. 30, 2004, now U.S. Pat. No. 7,150,824,which is a continuation of U.S. patent application Ser. No. 10/301,946,filed Nov. 22, 2002, now U.S. Pat. No. 6,841,065, which is acontinuation of U.S. patent application Ser. No. 09/800,982, filed Mar.7, 2001, now U.S. Pat. No. 6,540,909, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/220,540, filed Jul. 25, 2000.

FIELD OF THE INVENTION

The present invention relates to fluid filters, and more particularly, afluid filter cartridge having a pressure relief valve to provide anaccurate visual indicator as to the remaining life of the filtercartridge.

BACKGROUND OF THE INVENTION

It is well known to utilize fuel filter assemblies to filter fuel for acombustible engine of a motor vehicle. Such fuel filter assembliescomprise a variety of different orientations of the fuel filterassembly. For example, it is known to utilize sideways, downwardly, andupwardly mounted canisters having a paper filter media enclosed in thecanister. With respect to upwardly mounted fuel assemblies, prior artfiltration devices have been known to draw fuel into the filter assemblyby use of a pump on the outlet side of the filter assembly. The fuel isdirected downward into a lower chamber of the filter assembly whereinthe fuel flow proceeds upward into an upper filter chamber of the filterassembly. The fuel may then be contained and sealed by a transparentfilter cover or closure and a filter mount which may separate the lowerchamber from the upper chamber.

Within the filter chamber of the filter assembly, the filter assemblymay provide a filter canister comprised of a filter media circling acentral filter tube that is contained by filter end caps at the top andbottom of the filter media. The end caps are sealed to the edges of thefilter media to preclude any possible leak paths at the ends of thefilter canister. The filter media typically comprises a porous papermaterial that may be pleated or concentrically wound so as to direct thefluid through the filter media. The filter media removes and retainsundesirable contaminants within and on the media.

As fluid enters the filter chamber, the fuel level rises and passesthrough from the outside to the inside of the filter media. The fuelthen flows downward into a central passage located along the centralaxis of the canister. The central passageway is in communication with afuel outlet wherein the fuel passes outwardly from the filter assembly.

During the filtering process, the fuel is either drawn into the filterchamber by a vacuum or pushed into the filter chamber by pressure untilthe fuel finds a path through the filter media. As the fuel flowsthrough the filter, dirt and other contaminants larger than the porousopenings in the filter media, are trapped and retained by the filtermedia. These contaminants plug or clog the porous holes in the filtermedia and restrict or close the paths used by the flowing fuel. The fuelis then forced to seek other open and less restrictive flow openingswhich are available above the level of the fuel by climbing the heightof the filter and accessing the clean areas of the filter media. Thisprocess of clogging and climbing continues until the filter media iscompletely immersed in the flowing fuel.

Even though the filter media may be completely immersed in the flowingfluid, the incoming fuel continues to pass through the filter media. Itis not until the filter media becomes greatly clogged that the filtermedia needs to be replaced. This is a problem since the user generallyviews the height of the fuel in the filter chamber to see if the filtermedia is clogged. If the filter media is completely immersed in fuel,the user generally believes that the filter media needs to be replaced.Therefore, this type of system may lead to premature replacement of thefilter media.

It would be desirable to provide a fuel filter assembly that provides anaccurate indication as to the remaining usefulness of the filter media.

SUMMARY OF THE INVENTION

The invention provides a filter cartridge that includes a substantiallycylindrical filter media and a pressure relieving structure. The filtermedia is adapted to allow fluid to pass from an exterior of the filtermedia to an interior of the filter media. The pressure relievingstructure is disposed at an upper end of the filter media, and thepressure relieving structure opens when a predetermined pressure levelis established across the filter media to maintain the predeterminedpressure across the filter media.

The filter cartridge may include a top cap that is disposed at the upperend of the filter media and a bottom cap disposed at the lower end ofthe filter media and having an opening adapted to receive a fluidoutlet. Furthermore, a divider having an upper end connected to the topcap and an open lower end may be positioned adjacent to the exterior ofthe cylindrical filter media.

The pressure relieving structure may include a restrictive filter mediathat is more restrictive to fluid flow than the filter media to preventthe flow of the fluid and/or air/vapor through the restrictive filtermedia until the pressure across the filter media reaches thepredetermined pressure level, wherein the fluid and/or air/vapor passesthrough the restrictive filter media.

Alternatively, the pressure relieving structure may include a reliefvalve provided on the top cap. The relief valve may be seated in anaperture that extends through the top cap to the interior. Furthermore,the top cap may have a sheet of filter media may be disposed within thecup portion and covering the aperture to prevent unfiltered fluid frompassing through to the interior.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like referenced numerals refer to like parts throughout severalviews and wherein:

FIG. 1 is a schematic drawing showing the fluid flow path and the normalrising fluid path of a prior art fuel filter assembly;

FIG. 2 is a schematic drawing showing the rising fluid level in thefluid filter assembly of the present invention;

FIG. 3 is a schematic drawing showing a segment of filter media beingutilized above a relief valve in the fluid filter assembly of thepresent invention;

FIG. 4 is a schematic drawing showing a segment of filter media beingutilized underneath the relief valve in the fluid filter assembly of thepresent invention;

FIG. 5 is a schematic drawing of a hang down fluid filter assembly ofthe present invention;

FIG. 6 is a schematic drawing showing a restrictive media being utilizedas a relief valve in the fluid filter assembly of the present invention;

FIG. 7 is a bottom view of the filter element in the fluid filterassembly of the present invention;

FIG. 8 is a sectional view of the filter element in the fluid filterassembly of the present invention taken in the direction of arrows 9-9in FIG. 8;

FIG. 9 is an exploded view of the relief valve shown in the top of thefilter element in the fluid filter assembly of the present invention;

FIG. 10 is a sectioned perspective view of the relief valve shown in thetop of the filter element in the fluid filter assembly of the presentinvention;

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, the present invention will now be describedin detail with reference to the preferred embodiment.

FIG. 2 shows a fluid filter assembly 10 of the present invention in itspreferred form. The fluid filter assembly 10 is best suited forfiltering and processing diesel fuel, but the fluid filter assembly 10may also be utilized with other fluids, such as gasoline, oil, water,antifreeze, etc. The fluid filter assembly 10 is mounted verticallyupright and provides a closed housing 12, a lower fluid storage chamber16, and an upper filter chamber 17. A fluid inlet 14 is in communicationwith the lower fluid storage chamber 16, which is in communication withthe upper filter chamber 17 through a passageway 15. A filter element 20is housed within the upper filter chamber 17 of the housing 12 forfiltering a fluid 19 to a fluid outlet 18. The fluid inlet 14 deliversfluid 19 into the housing 12 so that the fluid 19 may pass through thefilter element 20 and out the fluid outlet 18. A relief valve 38 mountedin the top of the filter element 20 opens when the pressure level acrossthe filter element 20 reaches a predetermined level. A relief valvefilter 40 filters fluid 19 that passes through the relief valve 38.Preferably, the relief valve filter 40 is mounted below the relief valve38, as shown in FIG. 4, but alternatively, the relief valve filter 40may be mounted above the relief valve 38, as shown in FIG. 3.

To filter contaminants from the fluid 19, the filter element 20 isfabricated from a pleated porous paper material. The filter element 20encircles a central filter tube 22 and is contained by a top and bottomend cap 24, 26, respectively, as seen in FIGS. 2 and 7-10. The top andbottom end caps, 24, 26 are sealed to the edges of the filter element 20to preclude any possible leak paths at the ends of the filter element20. A flexible seal 28 is provided on the bottom end cap 26 of thefilter element 20 to create a seal between the central filter tube 22and an inner core 43 of the filter element 20 and ensure that unfilteredfluid 19 does not leak into or escape through the fluid outlet 18. Thefilter element 20 is preferably pleated or concentrically wound but mayalso be arranged in any of the ways known to one familiar withfiltration construction so as to direct the fluid 19 through the filterelement 20. In addition, the filter element 20 may be fabricated from ahydrophobic filter material to filter out water from the fluid 19.

The portion of the housing 12 between the filter element 20 and an outerwall 37 of the upper filter chamber 17 of the housing 12 is preferablydivided by a substantially frusto-conical divider 30. The divider 30 hasa top portion 32 that is either integrally or sealingly connected to thetop end cap 24 of the filter element 20. The divider 30 also has abottom portion 33 that extends downward toward the bottom of the filterelement 20, while also tapering or flaring outward away from the filterelement 20. It should be noted that the present invention is not limitedto a frusto-conical divider 30, but rather, the divider 30 may also besubstantially cylindrical wherein the bottom portion of the divider 30may extend downward substantially parallel to the filter element 20. Inboth embodiments, the divider 30 essentially divides the upper filterchamber 17 of the housing 12 into an inner portion or region 34 and anouter portion or region 36. The inner portion 34 is the space containedbetween the outside or unfiltered side of the filter element 20 and theinner surface of the divider 30. The outer portion 36 is the spacecontained between the outer surface of the divider 30 and the innersurface of the outer wall 37 of the upper filter chamber 17 of thehousing 12. The inner and outer portions 34, 36 remain in fluidcommunication at the bottom portion of the upper filter chamber 17 ofthe housing 12.

In order to maintain and relieve the pressure in the upper filterchamber 17 of the housing 12, a relief valve 38 is mounted in the topend cap 24 of the filter element 20. The top end cap 24 is fabricatedfrom a thin metallic material having a shape complementary to the top ofthe filter element 20. The top end cap 24 has a substantially circularconfiguration with sidewalls 39 that extend downward from its peripheryto sealingly connect to and cover the top of the filter element 20. Thetop end cap 24 also has a centrally located recessed portion 41 which isreceived by and complementarily engages the inner core 43 of the filterelement 20.

The recessed portion 41 of the top end cap 24 is formed by two layers ofthin metallic material. A first inner layer 45 is integrally connectedto the sidewalls 39 and the portion of the top end cap 24 that extendsover the top of the filter element 20. A second outer layer 47 of therecessed portion 41 is formed by a substantially cylindrical cup that isconnected to and complementarily engages the inner layer 45 of therecessed portion 41. The inner layer 45 of the recessed portion 41 has araised portion 49 relative to the outer layer 47. The outer layer 47 hasfour apertures 51 that extend therethrough and align directly under theraised portion 49 of the inner layer 45 of the recessed portion 41. Asheet of filter media 53 lies between the inner layer 45 and the outerlayer 47 of the recessed portion 41 so as to cover the four apertures 51extending through the outer layer 47.

The raised portion 49 of the inner layer 45 provides two apertures 55,57 extending therethrough. The larger of the two apertures 55 receives aflexible valve member 58 having an inverted mushroom-shapedconfiguration. The stem portion 59 of the mushroom-shaped configurationis disposed within the larger aperture 55. The head portion 61 of theflexible member 58 extends across the underside of the raised portion 49of the inner layer 45 such that the head portion 61 of the flexiblemember 58 covers the smaller aperture 57. The smaller aperture 57 actsas a port such that when the pressure level across the filter element 20reaches a predetermined level, the head portion 61 of the flexiblemember 58 flexes away from the smaller aperture 57 thereby allowingfluid 19 and/or air/vapor from the unfiltered side of the filter element20 to pass through the smaller aperture 57. Fluid 19 will only passthrough the smaller aperture 57 after all of the air/vapor has firstpassed through the smaller aperture 57. The fluid 19 and/or air/vaporpasses through the sheet of filter media 53 and through the fourapertures 51 in the outer layer 47 of the recessed portion 41 to thefiltered side of the filter element 20. Although the patentable subjectmatter may be limited to a relief valve 38 having the structure definedabove, Applicants consider the invention to include any relief valve 38having a structure that provides for the release of fluid 19 and/orair/vapor at a predetermined pressure level.

The relief valve 38 is normally closed until the pressure level acrossthe filter element 20 exceeds a predetermined level. When the reliefvalve 38 is closed, the air/vapor within the outer portion 36 of thehousing 12 is trapped thereby forcing the fluid level in the outerportion 36 to be lower than the fluid level in the inner portion 34.This occurs because as long as the filter element 20 is not clogged,air/vapor and fluid 19 within the inner portion 34 will pass through thefilter element 20 at a pressure less than the pressure level in whichthe relief valve 38 is to open. Once the pressure across the filterelement 20 exceeds the predetermined level due to the filter elementbeing sufficiently clogged, the relief valve 38 opens and allowsair/vapor and/or fluid 19 to pass from the outer portion 36 of thehousing 12 to the inner core 43 of the filter element 20.

In a secondary embodiment of the fluid filter assembly 10′, arestrictive filter media section 42 of the filter media 20′ is eitherintegrally formed on the top of the filter media 20′ or is attached tothe upper portion of the filter media 20′, as shown in FIG. 6. Therestrictive section 42 of the filter media 20′ acts in the same manneras the relief valve 38 and the relief valve filter 40 of the preferredembodiment, but the secondary embodiment does not require the divider30. The restrictive section 42 of the filter media 20′ only allowsair/vapor and/or fluid 19 to pass through the restrictive section 42once the pressure level across the filter element 20 exceeds apredetermined level. This ensures that the fluid level within thehousing 12 will remain at a level below the restrictive filter media 42.Once the predetermined pressure level is reached, air/vapor and/or fluidis allowed to pass through the restrictive filter media 42 therebyraising the fluid level and providing a visual indicator that the filtermedia 20′ needs replacement.

In yet another embodiment of the present invention, a divider 30″ and arelief valve 38″ may be utilized in conjunction with a hang down fluidfilter assembly 10″, as shown in FIG. 5. The structure in thisembodiment is similar to that of the preferred embodiment in that thedivider 30″ is sealingly connected to a top end cap 24″. The divider 30″extends downward along the bottom portion of the filter element 20 whileflaring outward from the filter element 20. A relief valve filter(although not shown in FIG. 5 but similar to that shown in FIGS. 3-4) ismounted in a portion of the central filter tube 22. The relief valvefilter is incorporated with the relief valve 38″ to prevent anyunfiltered fluid 19 from entering fluid outlet 18″. The relief valve 38″in the hang down fluid filter assembly 10″ works in the same manner asthe preferred embodiment. The divider 30″ forms an outer portion 34″ andan inner portion 32″ of the housing 12″ wherein the trapped air in theouter portion 34″ forces the fluid level in the outer portion 34″ to belower than the fluid level in the inner portion 32″. This allows thefilter element 20 to become completely clogged before reaching thepredetermined pressure level that will open the relief valve 38″. Oncethe relief valve 38″ opens, air/vapor passes through the relief valve38″ thereby allowing the fluid level in the outer portion 34″ to riseand provide a visual indicator that the filter element 20 needsreplacement.

In operation, the prior art device functions as depicted in FIG. 1.Fluid 19 enters the fluid inlet 14 of the fluid filter assembly 10 andaccumulates within the lower fluid storage chamber 16 of the housing 12.Fluid 19 flows through the passageway 15 leading to the upper filterchamber 17 wherein an unfiltered fluid level is established within theupper filter chamber 17. The fluid 19 is drawn into the upper filterchamber 17 by vacuum (as most commonly occurs in diesel fuel filters) orforced by low pressure (as seen in oil, antifreeze or many otherfilters) until it finds a path through the filter element 20. As thefilter element 20 becomes partially clogged, the restriction increasestemporarily overcoming the surface tension of fluid covering the unusedpores of the filter 20 element and causing a temporary flow of air/vaporthrough the filter element 20. As the air/vapor passes, it creates avoid on the outside of the filter element 20, and the fluid level risesto fill the void. The new fluid level allows flow through clean andunused pores of the filter element 20, and the restriction through thefilter element 20 reestablishes itself at a fluid level as previouslydescribed. Once the fluid level establishes itself, the surface tensionof the fluid 19 across the remaining pores of the filter element 20prevents the flow of air/vapor through the filter element 20 until, onceagain, the restriction increases to a level in which air/vapor is forcedthrough the filter element 20. This process continues as dirt and othercontaminants in the fluid 19, larger than the openings in the filterelement 20, are trapped and retained by the filter element 20 as thefluid 19 passes through the filter element 20. These contaminants plugor clog the holes in the filter element 20 and restrict and/or close thepaths used by the flowing fluid 19. The fluid 19 is forced to seek otheropen and less restrictive fluid openings that are above the level of thefluid 19, and therefore, the fluid 19 climbs up the height of the filterelement 20 and uses the clean areas of the filter element 20. Theprocess of clogging and climbing continues until the filter element 20is completely immersed in the flowing fluid 19. When the fluid levelreaches the top of the upper filter chamber 17, this has generally beena visible indication to the user to change the filter element 20. Theproblem with changing the filter element 20 at this point is that thefilter element 20 still allows for the passage of fluid 19 through thefilter element 20 even when the fluid level has risen to the top of theupper filter chamber 17. Therefore, if the filter element 20 is changedimmediately upon the fluid level rising to the top of the upper filterchamber 17, then the filter element 20 is being replaced prematurely.

During the operation of the preferred embodiment of the presentinvention, fluid 19 enters the fluid filter assembly 10 and the upperfilter chamber 17 in the same way as described in the prior art.However, by employing the divider 30 and incorporating the preset reliefvalve 38 in the top end cap 24, the fluid level can be made to riseapproximately in proportion to the plugging rate of the fuel element 20.This gives an accurate visual indicator as to the remaining life of thefilter element 20. In so doing, the incoming fluid 19 and air/vaporinitially behave as similarly described in the prior art. When the fluidlevel approaches the bottom of the divider 30, the fluid 19 continues torise between the filter element 20 and the inside surface of the divider30, which was previously defined as the inner portion 34 of the housing12, but the fluid 19 does not rise between the outer surface of thedivider 30 and the outer wall 37 of the housing 12, which was previouslydefined as the outer portion 36 of the housing 12. This is because thetrapped air/vapor in the outer portion 36 of the housing 12 prevents therise of fluid 19 into the outer portion 36 of the housing 12.

As to the inner portion 34 of the housing 12, fluid 19 and air/vapormove through the filter element 20 in a usual manner. The fluid levelcontinues to rise between the filter element 20 and the inside surfaceof the divider 30 as the filter element 20 becomes more clogged. Thiscontinues until the fluid 19 has risen to the full or nearly full heightof the filter element 20, as previously described. Once the filterelement 20 is completely saturated, the pressure differential across thefilter element 20 begins to increase with the increased clogging of thefilter element 20. Once this pressure differential reaches apredetermined level, preferably 5″ Hg, the relief valve 38 may open, andvapor/air may flow through the relief valve 38 while fluid 19 flowsthrough the filter element 20 since both present the same amount ofresistance to flow. As the pressure differential across the filterelement 20 begins to exceed the 5″ Hg point, the relief valve 38 becomesthe preferred flow path since its pressure differential is fixed at 5″Hg. Since air/vapor is closest to the relief valve 38, the air/vaporflows through the relief valve 38 first, and the fluid 19 follows. Thefluid level begins to rise in the outer portion 36 of the housing 12,thereby providing a visual indicator to the operator that the filterelement 22 is plugged. The relief valve filter 40 provided in the fluidpath of the relief valve 38 ensures that the fluid 19 that passesthrough the relief valve 38 is filtered. Once the user sees that thefluid level in the outer portion 36 of the housing 12 has risen to thetop of the upper filter chamber 17, the user knows to replace the filterelement 20.

In operation, the secondary embodiment, as depicted in FIG. 4, works ina similar manner as described in the preferred embodiment. The fluidlevel rises within the upper filter chamber 17, until it reaches therestrictive filter media 42 on the filter media 20′. When the fluidlevel reaches the restrictive media 42, the pressure differential acrossthe filter media 20′ must rise to a preferred level of 5″ Hg in orderfor the air/vapor and fluid 19 to pass through the restrictive media 42.The fluid level stops at a point just below the restrictive media 42until the filter media 20′ becomes so clogged that the pressuredifferential reaches the 5″ Hg level. At that point, air/vapor and fluid19 pass through the restrictive media 42, thus allowing the fluid levelto rise within the upper filter chamber 17 of the fluid filter assembly10′. The user may then use the risen fluid level as an indicator thatthe filter media 20′ needs to be replaced.

In operation, the alternative embodiment depicted in FIG. 5 works inexactly the same manner as described in the preferred embodiment. Theonly difference in the embodiment depicted in FIG. 5 is that the housing12″ is upside down, but the fluid level responds in the same manner asdescribed in the preferred embodiment.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, it is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims, the scope is to be accorded thebroadest interpretation so as to encompass all such modifications andequivalent structures as is permitted under the law.

1. A filter cartridge, comprising: a substantially cylindrical filtermedia adapted to allow fluid to pass from an exterior of said filtermedia to an interior of said filter media, said filter media having anupper end and a lower end; a pressure relieving structure disposed atsaid upper end of said filter media, and said pressure relievingstructure opening when a predetermined pressure level is establishedacross said filter media to maintain said predetermined pressure acrosssaid filter media.
 2. The filter cartridge of claim 1, furthercomprising: a top cap disposed at said upper end of said filter mediaand connected to said filter media; and a bottom cap disposed at saidlower end of said filter media and having an opening adapted to receivea fluid outlet.
 3. The filter cartridge of claim 2, further comprising:a divider positioned adjacent to said exterior of said filter media, thedivider having an upper end connected to said top cap and an open lowerend.
 4. The filter cartridge as stated in claim 2, said pressurerelieving structure further comprising: a restrictive filter media thatis more restrictive to fluid flow than said filter media to prevent theflow of said fluid and/or air/vapor through said restrictive filtermedia until the pressure across said filter media reaches saidpredetermined pressure level, wherein said fluid and/or air/vapor passesthrough said restrictive filter media.
 5. The filter cartridge as statedin claim 2, said pressure relieving structure further comprising: saidtop cap having a relief valve mounted therein for allowing said fluidand/or air/vapor to pass from said exterior of said filter media to saidinterior space when the pressure across said filter media reaches saidpredetermined level.
 6. The filter cartridge as stated in claim 5, saidpressure relieving structure further comprising: said top cap having anaperture formed therethrough for receiving said relief valve.
 7. Thefilter cartridge as stated in claim 6, said pressure relieving structurefurther comprising: a sheet of filter media connected to said top capand covering said aperture to prevent unfiltered fluid from passingthrough to said interior.
 8. A filter cartridge for use in a fluidfilter assembly having a vertical housing having a fluid inlet forcommunicating a fluid into the housing and a fluid outlet forcommunicating said fluid downstream of the housing, and the housinghaving an outer cover wherein at least a portion of the outer cover istransparent for viewing the level of the fluid in the housing, thefilter cartridge comprising: a substantially cylindrical filter mediaadapted to allow fluid to pass from an exterior of said filter media toan interior of said filter media, said filter media having an upper endand a lower end; a top cap disposed at said upper end of said filtermedia and connected to said filter media; a bottom cap disposed at saidlower end of said filter media and having an opening adapted to receivea fluid outlet; and a pressure relieving structure disposed at an upperend of said filter media, and said pressure relieving structure openingwhen a predetermined pressure level is established across said filtermedia, said pressure relieving structure allowing said fluid and/orair/vapor to pass through said relief valve when the pressure acrosssaid filter media reaches a predetermined level, wherein the release ofsaid pressure allows the level of said fluid to rise within the housingof the fluid filter assembly.
 9. The filter cartridge as stated in claim8, said pressure relieving structure further comprising: said top caphaving a restrictive filter media, and said restrictive filter mediabeing more restrictive to fluid flow than said filter media to preventthe flow of said fluid and/or air/vapor through said restrictive filtermedia until the pressure across said filter media reaches saidpredetermined pressure level, wherein said fluid and/or air/vapor passesthrough said restrictive filter media causing said fluid in said housingto rise, thereby providing an indicator as to the remaining usefulnessof said filter media.
 10. The filter cartridge of claim 8, furthercomprising: a divider positioned adjacent to said exterior of saidfilter media, said divider having an upper end connected to said top capand an open lower end, and said divider defining an interior regionbetween the outside of said filter media and an inner surface of saiddivider and an exterior region adjacent to the outer surface of saiddivider, wherein said interior region and said exterior region are incommunication at said open lower end of said divider.
 11. The filtercartridge as stated in claim 10, said pressure relieving structurefurther comprising: said top cap having an aperture extendingtherethrough to said interior; and a relief valve mounted within saidaperture.
 12. The filter cartridge as stated in claim 12, said pressurerelieving structure further comprising: a sheet of filter mediaconnected to said top cap and covering said aperture to preventunfiltered fluid from passing through to said interior.
 13. A filtercartridge for use in a fluid filter assembly having a vertical housinghaving a fluid inlet for communicating a fluid into the housing and afluid outlet for communicating said fluid downstream of the housing, andthe housing having an outer cover wherein at least a portion of theouter cover is transparent for viewing the level of the fluid in thehousing, the filter cartridge comprising: a substantially cylindricalfilter media adapted to allow fluid to pass from an exterior of saidfilter media to an interior space at least partially defined by saidfilter media; a top cap disposed at said upper end of said interiorspace and connected to said filter media; a bottom cap disposed at saidlower end of said interior space and having an opening adapted toreceive a fluid outlet; and a divider positioned adjacent to saidexterior of said cylindrical filter media, said divider having an upperend connected to said top cap and an open lower end, and said dividerdefining an interior region between the outside of said cylindricalfilter media and an inner surface of said divider and an exterior regionadjacent to the outer surface of said divider, wherein said interiorregion and said exterior region are in communication at said open lowerend of said divider; said top cap having a pressure relieving structurethat opens when a predetermined pressure level is established acrosssaid filter media, said relief valve allowing said fluid and/orair/vapor to pass through said relief valve when the pressure acrosssaid filter media reaches a predetermined level, wherein the release ofsaid pressure allows the level of said fluid to rise within the housingof the fluid filter assembly.
 14. The filter cartridge as stated inclaim 13, said pressure relieving structure further comprising: said topcap having a restrictive filter media, and said restrictive filter mediabeing more restrictive to fluid flow than said filter media to preventthe flow of said fluid and/or air/vapor through said restrictive filtermedia until the pressure across said filter media reaches saidpredetermined pressure level, wherein said fluid and/or air/vapor passesthrough said restrictive filter media causing said fluid in said housingto rise, thereby providing an indicator as to the remaining usefulnessof said filter media.
 15. The filter cartridge of claim 13, furthercomprising: a divider positioned adjacent to said exterior of saidfilter media, said divider having an upper end connected to said top capand an open lower end, and said divider defining an interior regionbetween the outside of said filter media and an inner surface of saiddivider and an exterior region adjacent to the outer surface of saiddivider, wherein said interior region and said exterior region are incommunication at said open lower end of said divider.
 16. The filtercartridge as stated in claim 15, said pressure relieving structurefurther comprising: said top cap having an aperture extendingtherethrough to said interior; and a relief valve mounted within saidaperture.
 17. The filter cartridge as stated in claim 16, said pressurerelieving structure further comprising: a sheet of filter mediaconnected to said top cap and covering said aperture to preventunfiltered fluid from passing through to said interior.
 18. The filtercartridge as stated in claim 13, further comprising: said cylindricalfilter media having a corrugated structure formed by a continuous sheetof filter media.